The present invention concerns a transmission control system for the data transmission system where a circuit is shared by a multiple number of devices by a sequential transmission control system and, more particularly, an improvement thereof so that the system as a whole does not fail even if a part of the devices fails.
In a system like an automobile where the devices to be controlled and the data source devices which provide data necessary for controlling such devices are scattered in a large number, a system of multiplex transmission via a communication control device is employed in order to simplify the connections between respective devices. The sequential transmission system is utilized often in order to reduce the number of communication circuits so that one circuit line is shared by respective communication control devices to carry out transmission in a predetermined sequence.
The conventional sequential transmission system, however, is detrimental in that, since a transmission control device cannot start transmission until the time the transmission control device one stage prior thereto has completed transmission, the data transmissioon through the whole system comes to fail if a part of the communication control devices fails for some reason.